﻿#region Copyright & License

//
// Author: Ian Davis <ian.f.davis@gmail.com> Copyright (c) 2007-2008, Ian Davs
//
// Portions of this software were developed for NUnit. See NOTICE.txt for more
// information. 
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//

#endregion

#region Using Directives

using System;
using Ensurance.Properties;

#endregion

namespace Ensurance.Constraints.Prefix
{
    /// <summary>
    /// NotConstraint negates the effect of some other constraint
    /// </summary>
    public class NotConstraint<T> : PrefixConstraint<T>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="NotConstraint"/> class.
        /// </summary>
        /// <param name="baseConstraint">The base constraint to be negated.</param>
        public NotConstraint( Constraint<T> baseConstraint )
            : base( baseConstraint )
        {
        }

        /// <summary>
        /// Test whether the constraint is satisfied by a given value
        /// </summary>
        /// <param name="actual">The value to be tested</param>
        /// <returns>
        /// True for if the base constraint fails, false if it succeeds
        /// </returns>
        public override bool IsSatisfiedBy( T actual )
        {
            Actual = actual;
            PassModifiersToBase();
            return !BaseConstraint.IsSatisfiedBy( actual );
        }

        /// <summary>
        /// Write the constraint description to a MessageWriter
        /// </summary>
        /// <exception cref="ArgumentNullException">if the message writer is null.</exception>
        /// <param name="writer">The writer on which the description is displayed</param>
        public override void WriteDescriptionTo( IMessageWriter writer )
        {
            if ( writer == null )
            {
                throw new ArgumentNullException( "writer" );
            }
            writer.WritePredicate( Resources.Not );
            BaseConstraint.WriteDescriptionTo( writer );
        }

        /// <summary>
        /// Write the actual value for a failing constraint test to a
        /// MessageWriter.
        /// </summary>
        /// <param name="writer">The writer on which the actual value is displayed</param>
        public override void WriteActualValueTo( IMessageWriter writer )
        {
            BaseConstraint.WriteActualValueTo( writer );
        }
    }
}